CO has been regarded by the scientific community as an environmental pollutant, asphyxiant and noxious health hazard from occupational or industrial exposure. Counter to this established toxicity and popular view of CO as a lethal substance, this laboratory and others have established a cyto- and tissue protective function of low concentrations of CO in cell culture and animal models of cell and tissue injury. While preliminary studies have established an anti-inflammatory effect of CO in rodents, less is known of the therapeutic potential of CO against polymicrobial sepsis. Furthermore, few studies have addressed this therapeutic potential in higher organisms such as non-human primates or humans. Despite indications that the therapeutic effects of CO in preventing tissue injury involve anti-inflammatory, anti-apoptotic, and anti-proliferative effects, the molecular mechanisms by which CO impacts cellular homeostasis remain incompletely understood. (Macro)-autophagy has gained recent attention as a fundamental cellular homeostatic mechanism which facilitates cellular survival under adverse conditions by recycling endogenous cellular macromolecules through lysosomal-dependent degradation. Autophagy was originally characterized in yeast, but the recent characterization of this process in mammals has raised intensive interest in its biological significance and potential as a therapeutic target. The endogenous regulation of autophagy as a either a protagonist or adaptive mechanism during disease pathogenesis is not well understood. Furthermore, nothing is known of how gaseous mediators such as CO may regulate this process. Thus, the characterization of mechanisms by which gaseous molecules such as CO could regulate autophagy and its relationship to tissue protection is a highly novel concept, with far-reaching implications on how CO could be adapted to clinical therapies. To examine these relationships, we propose the following hypothesis: CO confers cyto- and tissue protection in endotoxemia/sepsis by preserving cellular homeostasis and promoting bacterial clearance through molecular regulation and activation of the autophagic pathway. To address this hypothesis will we examine the following Specific Aims: Specific Aim 1: To determine the regulation and function of CO-induced autophagy in mediating the cytoprotective effects of CO in sepsis Specific Aim 2: To determine the mechanism by which CO-induced autophagic pathway mediates cytoprotection in experimental sepsis Specific Aim 3: To perform proof-of-concept studies for biomarker detection and therapeutic efficacy to assist in the planning of Phase 1/Phase IIa trial for therapeutic efficacy of CO in human sepsis PUBLIC HEALTH RELEVANCE: The mechanism by which low dose carbon monoxide provides cytoprotection in sepsis is poorly understood. Carbon monoxide induced autophagy may mediate its cytoprotection in sepsis. An improved understanding on how carbon monoxide induces autophagy will assist us to devise novel therapy in human sepsis in the future.